1. Field of the Invention
The present invention relates to computer input devices and more particularly to touch-sensitive computer input devices.
2. State of the Art
Touch-sensitive electronic keyboards are known, as for example from U.S. Pat. No. 3,691,555 issued Sep. 12, 1972 to Looschen (originally assigned to Burroughs Corporation). Also known are touch-sensitive pointing devices, exemplified by U.S. Pat. No. 4,550,221 issued Oct. 29, 1985 to Mabusth. Neither class of touch-sensitive input device, however, has achieved widespread public acceptance for use with personal computers.
In the case of touch-sensitive electronic keyboards, the lack of public acceptance suggests that typists found such keyboards to be harder to use, producing more errors. Touch-sensitive electronic keyboards do not in general allow the typist to as easily find a comfortable, accustomed "home position" and to detect mishits, i.e., mistaken keystrokes.
In the case of touch-sensitive pointing devices, such devices have typically offered only low pointing resolution, contrary to the computing trend of ever-increasing resolution.
Nevertheless, touch-sensitive computer input devices continue to offer the advantages of simplicity and reliability, as well as offering the potential for significant cost savings in relation to mechanical computer input devices. Furthermore, touch-sensitive computer input devices are not subject to size constraints imposed by mechanical considerations, an important factor in an era of increasing miniaturization.
An example of a particularly advantageous touch-sensitive computer input device is found in U.S. Pat. No. 5,194,862 issued Mar. 16, 1993 to Edwards (assigned to U.S. Philips Corporation), incorporated herein by reference. The patent discloses a touch sensor array built in a similar manner as a TFT active matrix liquid crystal display and which may be used as an overlay for the same. The touch sensor array offers comparable resolution as the liquid crystal display.